Network routers and switches are used to provide network connections in various modern computing environments. Network switches may connect computers within a network and network routers may connect multiple networks together. Networked computers are often spatially separated, e.g., tens of meters to one hundred meters or more apart in some deployments, and generally computers separated by several meters or more tend to operate using different power supplies. The system of network devices requires different isolations to support various applications, e.g., different power supplies of different computers provide a prescribed operating voltage for each computer but the power supplies of the different computers may be at different absolute potentials (DC voltages). As a result, network interfaces may not provide direct current (DC) connections between computers. Moreover, noise and spikes may be introduced onto the network wiring creating the potential for damage when networked computers are DC connected. For these and other reasons, some routers, switches, and computers, may be electrically isolated from other network devices connected to a network. In various applications, inexpensive, reliable, and space-efficient isolation devices, circuits, and systems are needed.